Larvae expressing Dscam22.214.171.124.Scer\UAS in the class I vpda neuron under the control of Scer\GAL4221 show considerable overlap of the vpda dendrites with the branches of the class III v'pda neuron, as occurs in wild type.
Larvae expressing Dscam126.96.36.199.Scer\UAS in both the class I vpda neuron and the class III v'pda neuron under the control of Scer\GAL4109(2)80 show very few overlaps between the two neurons (in contrast to wild type), with the two arbors segregating into nonoverlapping territories.
As early as 24 h after puparium formation (APF), wild-type dendrites form two overlapping dendritic arbors adjacent to each other at the anterior surface of the antennal lobe. These arbors represent glomeruli VA1d and DA1. By contrast, in projection neurons overexpressing DscamScer\UAS.188.8.131.52 under the control of Scer\GAL4Mz19, the two dendritic arbors are clearly separable by 24 h APF. At this early stage, dendrites extended over broader regions of the antennal lobe than those in the wild-type in all samples examined. During later developmental stage, the dendrites of wild-type Scer\GAL4Mz19-expressing projection neurons gradually refine and form two distinct glomerli by 50 h AFP. In contrast, the separation of dendrites persists in projection neurons overexpressing DscamScer\UAS.184.108.40.206. These phenotypes are seen before the maturation of synaptic connections in the antennal lobe.
Although DA1 and DC3 dendrites are at their normal positions in the antennal loves of flies expressing DscamScer\UAS.220.127.116.11 under the control of Scer\GAL4Mz19, VA1d dendrites are often shifted to a more ventral position on the anterior surface and are separated from DA1 dendrites by another glomerulus. Therefore, the overexpression of DscamScer\UAS.18.104.22.168 seems to cause a change in the spatial position of VA1d projection neuron dendrites in the adult antennal lobe.
Overexpression of DscamScer\UAS.22.214.171.124 under the control of Scer\GAL4unspecified in MARCM neuroblast clones affect the dendritic position of expressing neuron in the antennal lobe. The overexpression of DscamScer\UAS.126.96.36.199 in only the projection neurons innervating DA1 does not result in a ventral shift of the VA1d glomerulus. When DscamScer\UAS.188.8.131.52 is overexpressed in VA1d and DC3, VA1d dendrites are shifted in 42% of the brain hemispheres examined.
In some brain hemispheres where DscamScer\UAS.184.108.40.206 is overexpressed in projection neurons under the control of Scer\GAL4Mz19, the spatial position of the VA1d projection neuron dendrites shifted ventrally, away from the DA1 glomerulus. Notably, Or88a-axons shift to a ventral position accordingly in each case, maintaining the correct connections with the VA1d projection neuron dendrites. In those hemispheres in which DscamScer\UAS.220.127.116.11-overexpression does not induce a dendritic shift, Or88a axon targeting is normal. Overexpressing DscamScer\UAS.18.104.22.168 in projection neurons by Scer\GAL4Mz19 shifts the VA1d dendrites to a ventral position equivalent to VA1lm. In each hemisphere, when DscamScer\UAS.22.214.171.124 overexpression causes a ventral shift of VA1d dendrites, Or47b-axons shift to a dorsal position and innervate the glomerulus situated ectopically between DA1 and VA1d, avoiding the VA1d dendrites completely. In hemispheres where no projection neuron dendritic position shift occurs, Or47b-axons target normal positions. Note that for this VA1lm glomerulus, neither the pre- nor the postsynaptic partners have been subjected to any genetic modifications. Their positional shifts are the sole result of the expression of DscamScer\UAS.126.96.36.199 in projection neurons in glomeruli in neighbouring VA1lm.
Expression of Dscam188.8.131.52.Scer\UAS under the control of Scer\GAL4OK107 results in defects in the mushroom body of third instar larvae; multiple core fibers are seen in the peduncle (in contrast to wild type).